﻿// SimplexNoise for C#
// Author: Heikki Törmälä

//This is free and unencumbered software released into the public domain.

//Anyone is free to copy, modify, publish, use, compile, sell, or
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//binary, for any purpose, commercial or non-commercial, and by any
//means.

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//of this software dedicate any and all copyright interest in the
//software to the public domain. We make this dedication for the benefit
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//relinquishment in perpetuity of all present and future rights to this
//software under copyright law.

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namespace JBooth.VertexPainterPro.SimplexNoise
{
   /// <summary>
   /// Implementation of the Perlin simplex noise, an improved Perlin noise algorithm.
   /// Based loosely on SimplexNoise1234 by Stefan Gustavson <http://staffwww.itn.liu.se/~stegu/aqsis/aqsis-newnoise/>
   /// 
   /// </summary>
   public class Noise
   {
      /// <summary>
      /// 1D simplex noise
      /// </summary>
      /// <param name="x"></param>
      /// <returns></returns>
      public static float Generate(float x)
      {
         int i0 = FastFloor(x);
         int i1 = i0 + 1;
         float x0 = x - i0;
         float x1 = x0 - 1.0f;
         
         float n0, n1;
         
         float t0 = 1.0f - x0*x0;
         t0 *= t0;
         n0 = t0 * t0 * grad(perm[i0 & 0xff], x0);
         
         float t1 = 1.0f - x1*x1;
         t1 *= t1;
         n1 = t1 * t1 * grad(perm[i1 & 0xff], x1);
         // The maximum value of this noise is 8*(3/4)^4 = 2.53125
         // A factor of 0.395 scales to fit exactly within [-1,1]
         return 0.395f * (n0 + n1);
      }
      
      /// <summary>
      /// 2D simplex noise
      /// </summary>
      /// <param name="x"></param>
      /// <param name="y"></param>
      /// <returns></returns>
      public static float Generate(float x, float y)
      {
         const float F2 = 0.366025403f; // F2 = 0.5*(sqrt(3.0)-1.0)
         const float G2 = 0.211324865f; // G2 = (3.0-Math.sqrt(3.0))/6.0
         
         float n0, n1, n2; // Noise contributions from the three corners
         
         // Skew the input space to determine which simplex cell we're in
         float s = (x+y)*F2; // Hairy factor for 2D
         float xs = x + s;
         float ys = y + s;
         int i = FastFloor(xs);
         int j = FastFloor(ys);
         
         float t = (float)(i+j)*G2;
         float X0 = i-t; // Unskew the cell origin back to (x,y) space
         float Y0 = j-t;
         float x0 = x-X0; // The x,y distances from the cell origin
         float y0 = y-Y0;
         
         // For the 2D case, the simplex shape is an equilateral triangle.
         // Determine which simplex we are in.
         int i1, j1; // Offsets for second (middle) corner of simplex in (i,j) coords
         if(x0>y0) {i1=1; j1=0;} // lower triangle, XY order: (0,0)->(1,0)->(1,1)
         else {i1=0; j1=1;}      // upper triangle, YX order: (0,0)->(0,1)->(1,1)
         
         // A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
         // a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
         // c = (3-sqrt(3))/6
         
         float x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
         float y1 = y0 - j1 + G2;
         float x2 = x0 - 1.0f + 2.0f * G2; // Offsets for last corner in (x,y) unskewed coords
         float y2 = y0 - 1.0f + 2.0f * G2;
         
         // Wrap the integer indices at 256, to avoid indexing perm[] out of bounds
         int ii = i % 256;
         int jj = j % 256;
         
         // Calculate the contribution from the three corners
         float t0 = 0.5f - x0*x0-y0*y0;
         if(t0 < 0.0f) n0 = 0.0f;
         else {
            t0 *= t0;
            n0 = t0 * t0 * grad(perm[ii+perm[jj]], x0, y0); 
         }
         
         float t1 = 0.5f - x1*x1-y1*y1;
         if(t1 < 0.0f) n1 = 0.0f;
         else {
            t1 *= t1;
            n1 = t1 * t1 * grad(perm[ii+i1+perm[jj+j1]], x1, y1);
         }
         
         float t2 = 0.5f - x2*x2-y2*y2;
         if(t2 < 0.0f) n2 = 0.0f;
         else {
            t2 *= t2;
            n2 = t2 * t2 * grad(perm[ii+1+perm[jj+1]], x2, y2);
         }
         
         // Add contributions from each corner to get the final noise value.
         // The result is scaled to return values in the interval [-1,1].
         return 40.0f * (n0 + n1 + n2); // TODO: The scale factor is preliminary!
      }
      
      
      public static float Generate(float x, float y, float z)
      {
         // Simple skewing factors for the 3D case
         const float F3 = 0.333333333f;
         const float G3 = 0.166666667f;
         
         float n0, n1, n2, n3; // Noise contributions from the four corners
         
         // Skew the input space to determine which simplex cell we're in
         float s = (x+y+z)*F3; // Very nice and simple skew factor for 3D
         float xs = x+s;
         float ys = y+s;
         float zs = z+s;
         int i = FastFloor(xs);
         int j = FastFloor(ys);
         int k = FastFloor(zs);
         
         float t = (float)(i+j+k)*G3; 
         float X0 = i-t; // Unskew the cell origin back to (x,y,z) space
         float Y0 = j-t;
         float Z0 = k-t;
         float x0 = x-X0; // The x,y,z distances from the cell origin
         float y0 = y-Y0;
         float z0 = z-Z0;
         
         // For the 3D case, the simplex shape is a slightly irregular tetrahedron.
         // Determine which simplex we are in.
         int i1, j1, k1; // Offsets for second corner of simplex in (i,j,k) coords
         int i2, j2, k2; // Offsets for third corner of simplex in (i,j,k) coords
         
         /* This code would benefit from a backport from the GLSL version! */
         if(x0>=y0) {
            if(y0>=z0)
            { i1=1; j1=0; k1=0; i2=1; j2=1; k2=0; } // X Y Z order
            else if(x0>=z0) { i1=1; j1=0; k1=0; i2=1; j2=0; k2=1; } // X Z Y order
            else { i1=0; j1=0; k1=1; i2=1; j2=0; k2=1; } // Z X Y order
         }
         else { // x0<y0
            if(y0<z0) { i1=0; j1=0; k1=1; i2=0; j2=1; k2=1; } // Z Y X order
            else if(x0<z0) { i1=0; j1=1; k1=0; i2=0; j2=1; k2=1; } // Y Z X order
            else { i1=0; j1=1; k1=0; i2=1; j2=1; k2=0; } // Y X Z order
         }
         
         // A step of (1,0,0) in (i,j,k) means a step of (1-c,-c,-c) in (x,y,z),
         // a step of (0,1,0) in (i,j,k) means a step of (-c,1-c,-c) in (x,y,z), and
         // a step of (0,0,1) in (i,j,k) means a step of (-c,-c,1-c) in (x,y,z), where
         // c = 1/6.
         
         float x1 = x0 - i1 + G3; // Offsets for second corner in (x,y,z) coords
         float y1 = y0 - j1 + G3;
         float z1 = z0 - k1 + G3;
         float x2 = x0 - i2 + 2.0f*G3; // Offsets for third corner in (x,y,z) coords
         float y2 = y0 - j2 + 2.0f*G3;
         float z2 = z0 - k2 + 2.0f*G3;
         float x3 = x0 - 1.0f + 3.0f*G3; // Offsets for last corner in (x,y,z) coords
         float y3 = y0 - 1.0f + 3.0f*G3;
         float z3 = z0 - 1.0f + 3.0f*G3;
         
         // Wrap the integer indices at 256, to avoid indexing perm[] out of bounds
         int ii = Mod(i, 256);
         int jj = Mod(j, 256);
         int kk = Mod(k, 256);
         
         // Calculate the contribution from the four corners
         float t0 = 0.6f - x0*x0 - y0*y0 - z0*z0;
         if(t0 < 0.0f) n0 = 0.0f;
         else {
            t0 *= t0;
            n0 = t0 * t0 * grad(perm[ii+perm[jj+perm[kk]]], x0, y0, z0);
         }
         
         float t1 = 0.6f - x1*x1 - y1*y1 - z1*z1;
         if(t1 < 0.0f) n1 = 0.0f;
         else {
            t1 *= t1;
            n1 = t1 * t1 * grad(perm[ii+i1+perm[jj+j1+perm[kk+k1]]], x1, y1, z1);
         }
         
         float t2 = 0.6f - x2*x2 - y2*y2 - z2*z2;
         if(t2 < 0.0f) n2 = 0.0f;
         else {
            t2 *= t2;
            n2 = t2 * t2 * grad(perm[ii+i2+perm[jj+j2+perm[kk+k2]]], x2, y2, z2);
         }
         
         float t3 = 0.6f - x3*x3 - y3*y3 - z3*z3;
         if(t3<0.0f) n3 = 0.0f;
         else {
            t3 *= t3;
            n3 = t3 * t3 * grad(perm[ii+1+perm[jj+1+perm[kk+1]]], x3, y3, z3);
         }
         
         // Add contributions from each corner to get the final noise value.
         // The result is scaled to stay just inside [-1,1]
         return 32.0f * (n0 + n1 + n2 + n3); // TODO: The scale factor is preliminary!
      }



      
      public static byte[] perm = new byte[512] { 151,160,137,91,90,15,
         131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
         190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
         88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
         77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
         102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
         135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
         5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
         223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
         129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
         251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
         49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
         138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180,
         151,160,137,91,90,15,
         131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
         190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
         88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
         77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
         102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
         135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
         5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
         223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
         129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
         251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
         49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
         138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180 
      };
      
      private static int FastFloor(float x)
      {
         return (x > 0) ? ((int)x) : (((int)x) - 1);
      }
      
      private static int Mod(int x, int m)
      {
         int a = x % m;
         return a < 0 ? a + m : a;
      }
      
      private static float grad( int hash, float x )
      {
         int h = hash & 15;
         float grad = 1.0f + (h & 7);   // Gradient value 1.0, 2.0, ..., 8.0
         if ((h & 8) != 0) grad = -grad;         // Set a random sign for the gradient
         return ( grad * x );           // Multiply the gradient with the distance
      }
      
      private static float grad( int hash, float x, float y )
      {
         int h = hash & 7;      // Convert low 3 bits of hash code
         float u = h<4 ? x : y;  // into 8 simple gradient directions,
         float v = h<4 ? y : x;  // and compute the dot product with (x,y).
         return ((h&1) != 0 ? -u : u) + ((h&2) != 0 ? -2.0f*v : 2.0f*v);
      }
      
      private static float grad( int hash, float x, float y , float z ) {
         int h = hash & 15;     // Convert low 4 bits of hash code into 12 simple
         float u = h<8 ? x : y; // gradient directions, and compute dot product.
         float v = h<4 ? y : h==12||h==14 ? x : z; // Fix repeats at h = 12 to 15
         return ((h&1) != 0 ? -u : u) + ((h&2) != 0 ? -v : v);
      }
      
      private static float grad( int hash, float x, float y, float z, float t ) {
         int h = hash & 31;      // Convert low 5 bits of hash code into 32 simple
         float u = h<24 ? x : y; // gradient directions, and compute dot product.
         float v = h<16 ? y : z;
         float w = h<8 ? z : t;
         return ((h&1) != 0 ? -u : u) + ((h&2) != 0 ? -v : v) + ((h&4) != 0 ? -w : w);
      }
   }
}
